Air bled from one of the stages of the engine compressor, and
used for some function other than the operation of the engine.
Examples include: pressurization, deicing, air conditioning and
engine starting.
"There was a plane. I looked down at my watch and said
I sure hope the president is gone and out of the airspace by
now."
Source: Ed Borden, chairman of the Northwest
Alabama Regional Airport Board, who noticed US Air Force fighter
jets overhead while a Temporary Flight Restriction was in effect
over nearby Browns Ferry Nuclear Plant as President Bush was
visiting last Thursday. The fighters were scrambled to intercept a
Piper PA28 that had crossed into the TFR.